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Nanobodies are single variable domain antibodies isolated from camelids and are rapidly distinguishing themselves as ideal recognition elements in biosensors due to their comparative stability, ease of production and isolation, and high binding affinities. However, transducing analyte binding by nanobodies in real time is challenging, as most nanobodies do not directly produce an optical or electrical signal upon target recognition. Here, we report a general strategy to fabricate sensitive and selective electrochemical sensors incorporating nanobodies for detecting target analytes in heterogeneous media, such as cell lysate. Graphite felt can be covalently functionalized with recombinant HaloTag-modified nanobodies. Subsequent encapsulation with a thin layer of a hydrogel using a vapor deposition process affords encapsulated electrodes that directly display a decrease in current upon antigen binding, without added redox mediators. Differential pulse voltammetry affords clear and consistent decreases in electrode current across multiple electrode samples for specific antigen concentrations. The change in observed current vs increasing antigen concentration follows Langmuir binding characteristics, as expected. Importantly, selective and repeatable target binding in unpurified cell lysate is only demonstrated by the encapsulated electrode, with an antigen detection limit of ca. 30 pmol, whereas bare electrodes lacking encapsulation produce numerous false positive signals in control experiments.

The rise of additive manufacturing (i.e., 3D printing) as a key technology to rapidly fabricate materials with high quality and modifiable functionality is playing a major role in many scientific disciplines. Aided by advances in printer capabilities (e.g., resolution, material compatibility, print speed, etc) and the availability of affordable low-profile printers, 3D printing is rapidly becoming a staple piece of equipment in many chemistry research laboratories. One such area that 3D printing is having a profound impact is on analytical chemistry through the ability to rapidly print and prototype diagnostic devices for use in fields ranging from the environment to human health. This review describes recent advances in the fabrication of analytical devices which incorporate 3D printed sensing elements into electrochemical or physical sensors. Here we present an overview of the key milestones which have shaped the current state-of-the-art 3D printers as well as review progress made toward the development of sensors and their translation (and incorporation) into point-of-care devices such as wearables and soft robots.

The present work describes the synthesis of molecular imprinting polymer (MIP) and electrochemical sensing of Klebsiella pneumonia (K. pneumonia) bacteria by electrochemical technique. K. pneumonia has far reached ill effects on the human body, hence it is essential to monitor its levels. A MIP platform based on polypyrrole (PPy) was developed for electrochemical sensing of K. pneumonia to monitor its levels. The developed sensor has good sensitivity (3 μA ml CFU-cm⁻²), a low limit of detection (LOD) of 1.352 CFU ml⁻¹ in the linear detection range of 1 to 10⁵ CFU per ml. The molecular imprinting was carried out by polymerization of pyrrole in the presence of K. pneumonia and then removed the bacteria by ultrasonication to obtain the MIP. The fabrication of electrodes is done by electrophoretic deposition (EPD) of MIP onto the hydrolyzed ITO-coated glass surface. The detection was done by the electrochemical differential pulse voltammetry (DPV) technique. The synthesized final product is then characterized by Fourier transform infrared spectroscopy (FTIR) technique to understand its structure and confirm the successful synthesis of the desired MIP. The selectivity studies were performed against two other bacteria and different ions that are present in healthy human urine. To check the applicability in real sample studies, spiked urine samples were used.

There could not be a better time to launch a new venture in sensors, and the exploration of the biological interface with physicochemical devices offers especially exciting opportunities.

Longitudinal tracking of sleep metrics is important for detecting and managing various diseases, spanning cardiorespiratory disorders to dementia. However, at present, sleep monitoring primarily occurs in specialized medical facilities that are not conducive to long-term studies. In-home solutions either compromise user comfort or signal accuracy in tracking sleep variables and have not yet provided reliable longitudinal data. Here, we survey the current state of sleep trackers and highlight key shortcomings to provide guiding principles for improved sensor system design. We believe that human-centered design of multimodal, low-form-factor, comfortable sensing systems is needed for this increasingly-important area of human health monitoring.

Biomedical analysis needs fast reliable screening methods able to identify and also quantify substances of clinical interest. Diseases such as, cancer, diabetes, corona, influenza, stroke, cardiovascular diseases need an early detection. Therefore, developing new reliable electrochemical sensors may contribute to improving of the state of health and of the quality of life of people, by early detection of specific biomarkers able to predict the disease. Going to stochastic sensors for biomedical analysis is not just a trend. The screening tests are cost effective, and easy to be used, no sampling being needed before analysis.

Electrochemical aptamer-based (EAB) sensors encompass the only biosensor approach yet reported that is simultaneously: (1) independent of the chemical or enzymatic reactivity of its target, rendering it general; (2) continuous and lag-free; and (3) selective enough to deploy in situ in the living body. Consistent with this, in vivo EAB sensors supporting the seconds-resolved, real-time measurement of multiple drugs and metabolites have been reported, suggesting the approach may prove of value in biomedical research and the diagnosis, treatment, and monitoring of disease. However, to apply these devices in long-duration animal models, much less in human patients, requires that they be free of any significant pathogen load. Thus motivated, here we have characterized the compatibility of EAB sensors with standard sterilization and high-level disinfection techniques. Doing so, we find that, while many lead to significant sensor degradation, treatment with CIDEX OPA (0.55% ortho-phthalaldehyde) leads to effective disinfection without causing any detectable loss in sensor performance.

Sensors are considered to be an important vector for sustainable development. The demand to meet the needs of future generations is accelerating the development of intelligent sensor-systems integrated with internet of things (IoTs), fifth generation (5G) communication, artificial intelligence (AI) and machine learning (ML) strategies. The inclusion of 2D nanomaterials with the IoTs/AI/ML has revolutionized the diversified applications of sensors in healthcare, wearable electronics, safety, environment, defense, and agriculture. Owing to their unique physicochemical characteristics and surface functionalities, borophene and MXenes have emerged as advanced 2D-materials (A2M) to architect future-generation sensors. ML-AI based theoretical modeling has guided the research and development of A2M-sensors economically by reducing cost, human resources, and contamination. A2M-sensors are flexible, wearable, intelligent, biocompatible, portable, energy-efficient, self-sustained, point-of-care, and economical, which can drastically transform the conventional sensing strategies. This review provides an insight in to the state-of-the-art A2M-based physical, chemical, and biosensor to efficiently detect chemical species, gases/vapors, drugs, biomarkers/pathogens, pressure, metal ions, radiations, temperature, light, and humidity. Besides the fundamental challenges creating a gap between theoretical predictions, practical-evaluations, in-lab-technology, and commercial viability, their potential solutions, field-deployable prospects are addressed to realize commercialization, thereby ensuring ability of future generations to maintain sustainable communities.

Diode-type gas sensors using an anodized TiO₂ film and Pt electrodes modified with Au (Au(n)/Pt/TiO₂ (n: sputtering time of Au, 0–120 (s))) have been fabricated and their H₂-sensing properties have been investigated in this study. The surface modification of the Pt electrode with Au(n) drastically improved the H₂ response in dry air. The Au(20)/Pt/TiO₂ sensor showed the largest H₂ response in air among all the sensors tested, and the H₂ response in air was close to that in dry N₂. The H₂ response in air clearly increased with an increase in the humidity, and the H₂ response in wet air was comparable to that in wet N₂, especially under the higher humidified atmosphere (e.g., absolute humidity: 12.9 g m⁻³). The H₂ responses of all the sensors under every gaseous atmosphere are largely dependent on the applied voltage and operating temperature. In addition, the Au(20)/Pt/TiO₂ sensor showed an excellent selectivity against propane and propene. These results indicated that the optimal control of the amount of Au modified on the Pt electrode was quite important in improving both the H₂ response and selectivity in air as well as decreasing the oxygen-concentration dependence of the H₂ response, especially under wet atmosphere.

The presence of metals and semimetals can provide various information. In archeological samples, for instance, the investigation of metals can indicate the age of the objects, valuable information in historical studies; meanwhile, in cosmetics and food samples, their presence can indicate contamination which can cause severe problems to human health. In fuels, metals can cause environmental damage, economic loss, and damage car engine parts; therefore, their determination provides information about the fuel quality, while in gunshot residues samples they provide evidence of a crime scene and even help to identify the suspect, showing the considerable versatility of the results of a metal determination. Electrochemical techniques such as differential pulse voltammetry (DPV) and square wave voltammetry (SWV), voltammetry of immobilized microparticles (VIMP), and electrochemical impedance spectroscopy (EIS) have been used for these analyses due to their simplicity, sensitivity, low cost, and quickness. The paper presents the advances in electroanalysis performed in the last ten years (2011–2020) to determine metals in archeological, cosmetics, food, fuels, and gunshot residues samples.

YSZ-based potentiometric sensors employing thin CeO₂-added Au sensing electrodes (SEs) were fabricated by using a spin-coating method, and effects of the CeO₂ addition on their toluene sensing properties were examined. The sensor response (ΔE) to 50 ppm toluene of the sensors using 8 wt% CeO₂-added Au SEs tended to decrease with an increase in the number of spin-coating cycles (x: 5, 10, 15; i.e., the thickness of SEs). However, ΔE of the sensors using 24 wt% CeO₂-added Au SEs showed an opposite behavior to what was observed for 8 wt% CeO₂-added Au SEs. The sensor using the thickest SE (x: 15) showed the largest ΔE (e.g., ca. 212 mV for 50 ppm toluene) at 450 °C among all the sensors examined and responded even to 0.5 ppm toluene. ΔE exponentially increased with an increase in logarithmic toluene concentration in the range higher than 10 ppm. These obtained results indicate that electrochemical toluene oxidation proceeds at triple-phase boundaries in SE with gas (Au/CeO₂/gas) in addition to conventional TPBs (SE/YSZ/gas) in addition to the conventional interface at SE/YSZ/gas, because CeO₂ is a mixed ionic and electronic conductor. The electrochemical reactions at TPBs of the sensor were also discussed on the basis of the I–E characteristics and the electrochemical impedance properties.

Prompted by the increasing number of electrochemical biosensors reported in the literature, a wide range of lab-made potentiostats have been developed by researchers in recent years. While these devices are less costly than their commercial counterparts, they are typically single-plex and rely on non-integrated sample preparation or signal actuation devices. To address these limitations, we have designed a portable and fully integrated platform for point-of-care (PoC) electrochemical readout and actuation. This device performs standard voltammetric techniques and is controlled remotely by an accompanying smartphone application via Bluetooth Low Energy (BLE). This device supports both standard three-electrode and dual signal assays and can be extended to support multiple channels. Our device also integrates a portable heater and an electromagnet to facilitate away from lab sample heating and magnetic manipulation respectively. This device was used to detect nucleic acids and bacterial targets using single-stranded DNA probes and redox DNAzymes, respectively. The small form-factor and low cost of this device, in conjunction with the integration of peripheral instruments and native multiplex analysis capabilities, will enable electrochemical biosensing to be performed outside the research laboratory.

This study investigates the use of DC sputtering, physical vapor deposition as a facile method for creating ultralow loading, Au/C electrodes for use in the detection of As (III) in water. The sputtered nanofilm electrodes on carbon papers, substantially reduces the amount of Au consumed per electrode, <10 μg cm⁻², compared to use of wire, foil, or screen-printed electrodes. Linear stripping voltammetry (LSV) was chosen for analytical simplicity and ease of automation. Electrodes using Au nanoparticles supported on Vulcan XC 72 R carbon were also investigated but were not viable for LSV analysis due to capacitive current charging of the high surface area carbon. The DC sputtered, Au nanofilm electrodes were used to create calibration curves for concentrations of As (III) between 5 and 50 μg l⁻¹ and the standard addition method was used in a surface water sample with 5.5 μg l⁻¹ total As. Peak areas plotted against concentration displayed strong linear correlation with meaningful detection below the USEPA maximum contaminant level (MCL) of 10 μg l⁻¹. To our knowledge, this is the first study which utilizes the facile and mass manufacturable DC sputtering method to produce As (III) sensing electrodes. The results of this study have implications for the development of single use, low-cost nanofilm electrodes for field As (III) electroanalysis.